CN113013396A - Carbon-sulfur composite film, preparation method and application thereof - Google Patents
Carbon-sulfur composite film, preparation method and application thereof Download PDFInfo
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- H01M4/00—Electrodes
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- C01B17/00—Sulfur; Compounds thereof
- C01B17/02—Preparation of sulfur; Purification
- C01B17/06—Preparation of sulfur; Purification from non-gaseous sulfides or materials containing such sulfides, e.g. ores
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- C—CHEMISTRY; METALLURGY
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- H—ELECTRICITY
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- H—ELECTRICITY
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- H01M10/00—Secondary cells; Manufacture thereof
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- H—ELECTRICITY
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Abstract
The invention discloses a carbon-sulfur composite film, a preparation method and application thereof. The material can be applied to a plurality of fields such as battery anode materials, medicament synthesis and the like. When the lithium sulfur battery anode material is used as a battery anode material, a conductive agent and a binder are not required to be additionally used, so that the area capacity and the energy density of the lithium sulfur battery can be effectively improved, and the battery product is endowed with higher, more stable charge-discharge specific capacity and longer cycling stability; meanwhile, the dissolution of sulfur and discharge products in the electrolyte can be better inhibited, the shuttle effect is reduced, and the cycle stability and the capacity retention rate of the battery are improved. Compared with the traditional sulfur carrying method, the method for generating sulfur in situ has simple process, can realize that the sulfur is completely coated by carbon, and simultaneously leaves a certain gap, so that enough space is left for the volume change of the sulfur in the lithiation and delithiation processes, and the electrode pulverization is avoided.
Description
Technical Field
The invention relates to a carbon-sulfur composite film, and also discloses a preparation method and application thereof, belonging to the technical field of new materials.
Background
Lithium battery (Lithium battery) refers toA battery containing lithium (including metallic lithium, lithium alloy, lithium ion and lithium polymer) in an electrochemical system. Through development for many years, the lithium battery becomes the leading product in a secondary power supply, and the application level of the lithium battery generally reaches the specific capacity of the positive electrode of 250 mAh g-1Approaching the limit of the theoretical specific capacity of the lithium ion battery electrode material (about 300 mAh g)-1). However, with the rapid development of new energy technologies, the energy density of a common lithium ion battery is difficult to meet the requirements of the current high-capacity energy storage technology, and a novel lithium battery such as a lithium-sulfur battery appears in the market. The lithium-sulfur battery becomes one of the best choices of future power batteries by virtue of the advantages of high energy density, no pollution, low cost and the like. As early as 1962, Herbet et al first proposed the concept of using elemental sulfur as a new cathode material.
The lithium-sulfur battery is a lithium battery with sulfur as the positive electrode and metal lithium as the negative electrode. Theoretical energy density of the lithium-sulfur battery is 2600 Wh kg-1And the energy density is far higher than that of the current lithium ion battery. The theoretical specific capacity of elemental sulfur can reach 1675 mAh g-1The material is a known solid positive electrode material with the highest theoretical specific capacity. In addition, elemental sulfur has many advantages of low price, large storage capacity, no pollution and the like, so the lithium sulfur battery is considered to be a high-energy-density energy storage system with great development potential. Although lithium-sulfur batteries have so many advantages, elemental sulfur and the discharge product Li2Electrical insulation of S, volume expansion of sulfur during discharge, and polysulfide (Li) intermediate product of electrochemical reactionPSs) reduces the utilization of electrode active materials and the cycle life of the battery, and seriously hinders the commercialization of lithium-sulfur batteries.
In addition, the complexity of the sulfur-carrying process is also an important factor for restricting the commercial development of the lithium-sulfur battery. At present, the prior art generally adopts a two-step sulfur melting method to prepare a sulfur-carbon compound: the sulfur is first heated to 115 ℃ to melt it, allowing the liquid sulfur to enter the porous carbon voids, followed by a 300 ℃ heat treatment to remove sulfur that does not enter the porous carbon voids. The process is complex, needs vacuum pumping and heating treatment, and takes a long time.
In order to solve the problem of poor conductivity of elemental sulfur and discharge products thereof, a method of adding a nano conductive agent with a high specific surface is adopted at present, but the area sulfur-carrying capacity and the specific capacity of an electrode are reduced. In order to solve the problem of shuttle effect of polysulfide (LiPSs), conductive polymers (such as polypyrrole, polyaniline, polythiophene and the like) are used for coating a sulfur positive electrode; a porous intercalation with stronger adsorption capacity is also arranged between the diaphragm and the anode to prevent the shuttle effect of polysulfide; in addition, the technology is that an additive with strong adsorption capacity (such as nano lanthanum oxide, silicon dioxide and the like) is added into the positive electrode to adsorb polysulfide and inhibit the polysulfide from dissolving in the electrolyte. The methods objectively have a certain effect of inhibiting polysulfide from dissolving in electrolyte, can improve the cycling stability of the lithium-sulfur battery to a certain extent, but also have the problems of complex process, higher cost, reduction of the conductivity of a sulfur electrode, reduction of the electrochemical activity of reaction and the like, and are difficult to popularize in a commercialization process.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide the carbon-sulfur composite film which has high area sulfur loading and good sulfur coating effect;
the second purpose is to provide a preparation method of the carbon-sulfur composite film, so that elemental sulfur is generated in situ, the sulfur-carrying effect is optimized, and the sulfur-carrying process is simplified;
the third purpose is to provide the application of the carbon-sulfur composite film.
In order to achieve the above object, the present invention adopts the following technical solutions:
the invention firstly discloses a carbon-sulfur composite film, wherein the internal structure of the material is porous carbon coated elemental sulfur, the carbon is porous, and the elemental sulfur is distributed in pore channels of the carbon.
Preferably, the carbon-sulfur composite film is a self-supporting carbon-sulfur composite film which generates sulfur in situ, and the thickness of the film is 1-1000 μm.
More preferably, in the carbon-sulfur composite film, the mass percentage of the elemental sulfur is 10% -80%.
More preferably, the elemental sulfur is sulfur nanoparticles with a particle size of 1-1000 nm.
The invention also discloses a preparation method of the carbon-sulfur composite film, which comprises the following steps:
s1, mixing a sulfur precursor, a carbon precursor, a solvent, an adhesive and a defoaming agent, adding into a ball mill, and ball-milling to obtain slurry for tape casting;
s2, carrying out vacuum defoaming treatment on the slurry prepared in the step S1, and then carrying out tape casting on a casting machine to prepare a blank film;
s3, cutting the embryonic membrane prepared in the step S2 into pieces and then drying the embryonic membrane;
s4, performing high-temperature carbonization treatment on the dried embryonic membrane prepared in the step S3;
s5, soaking the film prepared in the step S4 in an oxidizing solution to oxidize the negative 2-valent sulfur into elemental sulfur in situ;
and S6, washing the film prepared in the step S5 for multiple times by deionized water, and then drying to obtain the carbon-sulfur composite film.
Preferably, in the step S1, the sulfur precursor is nano-sulfide particles, and the particle size of the particles is 1 to 1000 nm;
preferably, the carbon precursor is selected from one or more of sucrose, glucose, phenolic resin and asphalt, and the mass ratio of the carbon precursor to the sulfur precursor in the casting material is 1/20-20/1;
preferably, the solvent is one of water, acetone or alcohol, and the mass fraction of the solvent in the casting material is 40% -90%;
preferably, the adhesive is selected from one or more of polyvinyl butyral (co-vinyl alcohol-co-vinyl acetate), polyacrylamide, polyvinyl alcohol (PVA) and partially hydrolyzed polyvinyl alcohol (PVA), and the mass ratio of the sulfur precursor to the adhesive is 1/10-10/1;
preferably, the defoaming agent is n-butyl alcohol and accounts for 0.1-10% of the mass fraction of the casting material.
More preferably, in the step S1, the method further includes a plasticizer selected from one or more of polyethylene glycol, polyol and polyamine, and the mass ratio of the plasticizer to the sulfur precursor is 1/10 to 10/1, or 1/5 to 5/1, or 1/1 to 3/1.
More preferably, in the foregoing step S1, the method further includes a surfactant selected from: one or more of poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) block copolymer (PEO-PPO-PEO), polysorbate 80, and partially hydrolyzed polyvinyl alcohol (PVA), wherein the mass ratio of the surfactant to the carbon precursor is 1/100 to 100/1 or 1/10 to 10/1.
More preferably, in the step S1, the method further includes a reinforcing material, wherein the reinforcing material is selected from: one or more of carbon nanotubes, carbon fibers, graphene, and graphene oxide. The carbon-sulfur composite membrane reinforced by the reinforcing material can further improve the strength of the carbon-sulfur composite membrane, so that the carbon-sulfur composite membrane is not easy to break and deform.
Still preferably, in the step S1, the method further includes a dopant selected from the group consisting of: one or more of a nitrogen-containing precursor, a phosphorus-containing precursor, a boron-containing precursor and a sulfur-containing precursor. The doping agent can optimize the adsorption performance of the porous carbon material to sulfur, so that the cycle performance of the lithium-sulfur battery can be further optimized.
More preferably, in the step S2, the casting speed is 0.01 to 10m/min, and the blade height is 50 to 5000 μm.
More preferably, in step S4, the carbonization is performed at a temperature between 500 ℃ and 1500 ℃, and the carbonization is performed in a protective atmosphere, where the protective atmosphere is an atmosphere of nitrogen, helium, argon, or a mixture thereof, so as to avoid oxidation of the material in a high-temperature environment.
Still more preferably, in step S5, the oxidizing solution is one selected from iron sulfate, iron cyanide, iron chloride, iron ammine sulfate, sodium hypochlorite, and potassium permanganate.
In addition, the invention also discloses a method for using the carbon-sulfur composite film as the positive electrode material of various batteries, including but not limited to lithium-sulfur batteries, sodium-sulfur batteries or zinc-sulfur batteries. In addition, the film can be applied to various fields such as gunpowder, medicament, medicine synthesis and the like, and has very wide application field and wide application prospect.
The invention has the advantages that:
(1) the carbon-sulfur composite film is a porous carbon-coated elemental sulfur carbon-sulfur composite film, the thickness of the carbon-coated elemental sulfur carbon-sulfur composite film is 1-1000 micrometers (micrometers), the area sulfur carrying amount can be adjusted by controlling the film thickness, and when the thickness is 100 micrometers, the area sulfur carrying amount is 5mg/cm, so that the application requirements of the industrial market can be well met;
(2) the carbon-sulfur composite film can be used as a positive electrode material of a lithium-sulfur battery, and a conductive agent and a binder are not required to be additionally used in the using process, so that the area capacity and the energy density of the lithium-sulfur battery can be effectively improved, and the product is endowed with higher, more stable charge-discharge specific capacity and longer cycling stability;
(3) the carbon-sulfur composite film of the porous carbon-coated elemental sulfur is used as a battery anode material, can better inhibit sulfur and discharge products from being dissolved in electrolyte, and inhibit shuttle effect, thereby further improving the cycle stability and capacity retention rate of the lithium-sulfur battery;
(4) the preparation method disclosed by the invention is easy to realize, controllable in process and low in cost, and has good industrial popularization and market application prospects. Compared with the traditional sulfur carrying method, the method for generating sulfur in situ is novel and unique, not only has simple process, but also can realize that sulfur is completely coated by carbon, and simultaneously a certain gap is left, so that enough space is left for the volume change of sulfur in the processes of lithiation and delithiation, and the electrode pulverization is avoided.
Drawings
FIG. 1 is a thermogravimetric plot of a carbon sulfur composite thin film prepared in example 1 of the present invention;
FIG. 2 is an SEM image of a carbon-sulfur composite thin film prepared in example 1 of the present invention;
fig. 3 is a graph showing the change in specific discharge capacity at 0.5C of the lithium-sulfur battery manufactured in example 7.
Detailed Description
The invention is described in detail below with reference to the figures and the embodiments.
Example 1
The carbon-sulfur composite film of the present embodiment has an internal structure of carbon-coated sulfur nanoparticles, wherein the carbon is porous, and elemental sulfur is a sulfur nanoparticle and is distributed in a pore channel of the carbon.
The preparation method comprises the following specific steps:
s1, preparing slurry
120 g of nano zinc sulfide powder (average particle size 50 nm), 100 g of water-soluble phenol resin, 200mL of water, 10g of water-soluble polyvinyl alcohol powder, 5g of glycerol, 3g of poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) block copolymer (PEO-PPO-PEO) and 40g of n-butanol were put into a ball mill pot and ball-milled for 2 hours (300 rpm, using 400 g of alumina balls each having a diameter of 4 mm) to obtain a uniformly mixed casting slurry.
S2 casting
Before casting, the casting slurry was degassed under vacuum for 30 minutes to remove air bubbles. Placing on a casting machine for casting molding, wherein the casting speed is 0.5m/min, and the height of a scraper is 1000 mu m. After drying at room temperature for 12 hours, the cast embryonic film was cut into 10cm by 10cm square pieces.
S3, drying
And (3) putting the square sheet embryonic membrane into a gel discharging furnace, and drying and discharging gel for 4 hours at 150 ℃.
S4, carbonization
And (5) putting the square sheet-shaped embryonic membrane subjected to the rubber removal in the step (S3) into an electric furnace, heating to 900 ℃ in a nitrogen atmosphere, carbonizing for 2 hours, and cooling after carbonization. Wherein the heating rate is 2 ℃/min, and the cooling rate is 5 ℃/min.
S5 preparation of elemental sulfur by in-situ oxidation
The carbonized square sheet-like film obtained in step S4 was immersed in 800g of a saturated aqueous ferric nitrate solution for 2 hours, using Fe3+The sulfur with the valence of minus 2 is oxidized into elemental sulfur.
And S6, washing the membrane obtained in the step S5 with deionized water for 3 times, putting the membrane into an oven, and drying the membrane for 6 hours at 80 ℃ to obtain the carbon-sulfur composite membrane.
Through detection, the carbon-sulfur composite membrane of the embodiment has the membrane thickness of 100 μm and the area sulfur carrying capacity of 5mg/cm2。
Example 2
The carbon-sulfur composite film of the present embodiment has an internal structure of carbon-coated sulfur nanoparticles, wherein the carbon is porous, and the sulfur nanoparticles are distributed in the pore channels of the carbon.
The preparation method comprises the following specific steps:
s1, preparing slurry
122 g of nano copper sulfide powder (average particle size 50 nm), 150 g of sucrose, 200mL of water, 10g of water-soluble polyvinyl alcohol powder, 7g of ethylene glycol, 3g of poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) block copolymer (PEO-PPO-PEO) and 40g of n-butanol were put into a ball mill and ball-milled for 2 hours (300 rpm, using 400 g of alumina balls, each diameter being 4 mm) to obtain a uniformly mixed casting slurry.
S2 casting
Before casting, the casting slurry was degassed under vacuum for 30 minutes to remove air bubbles. Placing on a casting machine for casting molding, wherein the casting speed is 0.8m/min, and the height of a scraper is 1000 mu m. After drying at room temperature for 12 hours, the cast embryonic film was cut into 10cm by 10cm square pieces.
S3, drying
And (3) putting the square sheet embryonic membrane into a gel discharging furnace, and drying and discharging gel for 6 hours at 120 ℃.
S4, carbonization
And (5) putting the square sheet-shaped embryonic membrane subjected to the rubber removal in the step (S3) into an electric furnace, heating to 600 ℃ in a nitrogen atmosphere, carbonizing for 4 hours, and cooling after carbonization. Wherein the heating rate is 1 ℃/min, and the cooling rate is 5 ℃/min.
S5 preparation of elemental sulfur by in-situ oxidation
And (4) soaking the carbonized square sheet membrane obtained in the step (S4) in 1000g of saturated sodium hypochlorite aqueous solution for 2 hours, and oxidizing the negative 2-valent sulfur into elemental sulfur by using sodium hypochlorite.
And S6, washing the membrane obtained in the step S5 with deionized water for 3 times, putting the membrane into an oven, and drying the membrane for 6 hours at 80 ℃ to obtain the carbon-sulfur composite membrane.
Through detection, the carbon-sulfur composite membrane is 100 mu m, and the area sulfur-carrying capacity is 5mg/cm2。
Example 3
The carbon-sulfur composite film of the embodiment is a carbon-sulfur composite film, the internal structure is carbon-coated sulfur nanoparticles, and carbon in the carbon-sulfur composite film is porous, and the sulfur nanoparticles are distributed in the pore channels of the carbon.
The preparation method comprises the following specific steps:
s1, preparing slurry
120 g of nano zinc sulfide powder (average particle diameter 100 nm), 50 g of alcohol-soluble phenol resin, 200mL of ethanol, 10g of polyvinyl butyral, 7g of 1, 2-propanediol, 4g of polysorbate 80 and 40g of n-butanol were put into a ball mill and ball-milled for 2 hours (300 rpm, using 400 g of alumina balls, each diameter being 4 mm) to obtain a casting slurry which was uniformly mixed.
S2 casting
Before casting, the casting slurry was degassed under vacuum for 30 minutes to remove air bubbles. Placing the mixture on a casting machine for casting molding, wherein the casting speed is 1m/min, and the height of a scraper is 1000 mu m. After drying at room temperature for 12 hours, the cast embryonic film was cut into 10cm by 10cm square pieces.
S3, drying
And (3) putting the square sheet embryonic membrane into a gel discharging furnace, and drying and discharging gel for 5 hours at 140 ℃.
S4, carbonization
And (5) putting the square sheet-shaped embryonic membrane subjected to the rubber removal in the step (S3) into an electric furnace, heating to 800 ℃ in a nitrogen atmosphere, carbonizing for 3 hours, and cooling after carbonization. Wherein the heating rate is 1 ℃/min, and the cooling rate is 3 ℃/min.
S5 preparation of elemental sulfur by in-situ oxidation
The carbonized square sheet-like film obtained in step S4 was immersed in 800g of a saturated aqueous solution of ferric chloride for 2 hours using Fe3+The sulfur with the valence of minus 2 is oxidized into elemental sulfur.
And S6, washing the membrane obtained in the step S5 with deionized water for 3 times, putting the membrane into an oven, and drying the membrane for 6 hours at 80 ℃ to obtain the carbon-sulfur composite membrane.
Through detection, the carbon-sulfur composite membrane is 100 mu m, and the area sulfur-carrying capacity is 5mg/cm2。
Example 4
The carbon-sulfur composite film of this embodiment is a carbon-fiber-reinforced carbon-sulfur composite film, and the internal structure of this carbon-sulfur composite film is carbon-coated sulfur nanoparticles, and carbon among them is porous, and the sulfur nanoparticles distribute in the pore of carbon.
The preparation method comprises the following specific steps:
s1, preparing slurry
120 g of nano zinc sulfide powder (average particle size 50 nm), 120 g of soluble mesophase pitch, 200mL of water, 0.1g of carbon fiber short fibers or carbon fiber powder, 10g of water-soluble polyvinyl alcohol powder, 5g of glycerol, 3g of poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) block copolymer (PEO-PPO-PEO) and 40g of n-butanol were put into a ball mill tank and ball-milled for 2 hours (300 rpm, using 400 g of alumina balls, each diameter being 4 mm) to obtain a uniformly mixed casting slurry.
S2 casting
Before casting, the casting slurry was degassed under vacuum for 30 minutes to remove air bubbles. Placing on a casting machine for casting molding, wherein the casting speed is 1m/min, and the height of a scraper is 500 mu m. After drying at room temperature for 12 hours, the cast embryonic film was cut into 10cm by 10cm square pieces.
S3, drying
And (3) putting the square sheet embryonic membrane into a gel discharging furnace, and drying and discharging gel for 4 hours at 150 ℃.
S4, carbonization
And (5) putting the square sheet-shaped embryonic membrane subjected to the rubber removal in the step (S3) into an electric furnace, heating to 900 ℃ in a nitrogen atmosphere, carbonizing for 2 hours, and cooling after carbonization. Wherein the heating rate is 2 ℃/min, and the cooling rate is 5 ℃/min.
S5 preparation of elemental sulfur by in-situ oxidation
The carbonized square sheet-like film obtained in step S4 was immersed in 800g of a saturated aqueous ferric nitrate solution for 2 hours using Fe3+The sulfur with the valence of minus 2 is oxidized into elemental sulfur.
And S6, washing the membrane obtained in the step S5 with deionized water for 3 times, putting the membrane into an oven, and drying the membrane for 6 hours at 80 ℃ to obtain the carbon-sulfur composite membrane.
Through detection, the carbon-sulfur composite membrane of the embodiment has the membrane thickness of 60 μm and the area sulfur loading amount of 2.5mg/cm2. Meanwhile, the carbon fiber of the present embodimentThe reinforced carbon-sulfur composite film can further improve the strength of the carbon-sulfur composite film, so that the composite film has better mechanical property and is not easy to break and deform.
Example 5
The carbon-sulfur composite film of the embodiment is a nitrogen-doped carbon-sulfur composite film, the internal structure of the carbon-sulfur composite film is carbon-coated sulfur nanoparticles, carbon in the carbon-sulfur composite film is porous, and the sulfur nanoparticles are distributed in pore channels of the carbon.
The preparation method comprises the following specific steps:
s1, preparing slurry
120 g of nano zinc sulfide powder (average particle diameter 50 nm), 150 g of glucose, 200mL of water, 0.3g of melamine, 10g of water-soluble polyvinyl alcohol powder, 5g of glycerol, 3g of poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) block copolymer (PEO-PPO-PEO) and 40g of n-butanol were put into a ball mill and ball-milled for 2 hours (300 rpm, using 400 g of alumina balls each having a diameter of 4 mm) to obtain a uniformly mixed casting slurry.
S2 casting
Before casting, the casting slurry was degassed under vacuum for 30 minutes to remove air bubbles. Placing on a casting machine for casting molding, wherein the casting speed is 0.5m/min, and the height of a scraper is 800 mu m. After drying at room temperature for 12 hours, the cast embryonic film was cut into 10cm by 10cm square pieces.
S3, drying
And (3) putting the square sheet embryonic membrane into a gel discharging furnace, and drying and discharging gel for 4 hours at 150 ℃.
S4, carbonization
And (5) putting the square sheet-shaped embryonic membrane subjected to the rubber removal in the step (S3) into an electric furnace, heating to 900 ℃ in an argon atmosphere, carbonizing for 2 hours, and cooling after carbonization. Wherein the heating rate is 2 ℃/min, and the cooling rate is 5 ℃/min.
S5 preparation of elemental sulfur by in-situ oxidation
And (4) soaking the carbonized square sheet membrane obtained in the step (S4) in 1000ml of water, and continuously introducing chlorine for 2 hours to oxidize the negative 2-valent sulfur into elemental sulfur by using the chlorine.
And S6, washing the membrane obtained in the step S5 with deionized water for 3 times, putting the membrane into an oven, and drying the membrane for 6 hours at 80 ℃ to obtain the carbon-sulfur composite membrane.
Through detection, the carbon-sulfur composite membrane of the embodiment has the membrane thickness of 80 μm and the area sulfur loading amount of 4mg/cm2. The carbon-sulfur composite film is a nitrogen-doped carbon-sulfur composite film, wherein the adsorption performance of nitrogen to sulfur is better, so that the cycle performance of the lithium-sulfur battery can be further optimized.
Example 6
The carbon-sulfur composite film of the present embodiment has an internal structure of carbon-coated sulfur nanoparticles, wherein the carbon is porous, and the sulfur nanoparticles are distributed in the pore channels of the carbon.
The specific preparation steps are exactly the same as those in example 1, except that: step S1 also includes the addition of a nitrogen-containing dopant: 1g of melamine.
Through detection, the carbon-sulfur composite membrane of the embodiment has the membrane thickness of 100 μm and the area sulfur carrying capacity of 5mg/cm2. The carbon-sulfur composite film is a nitrogen-doped carbon-sulfur composite film, wherein the adsorption performance of nitrogen to sulfur is better, so that the cycle performance of the lithium-sulfur battery can be further optimized.
Example 7
In this example, a lithium sulfur battery was prepared using the carbon sulfur composite membrane prepared in example 1 as a positive electrode material.
Referring to the prior art battery assembly process, the manufacturing process of the lithium-sulfur battery needs to be specifically described as follows: and no adhesive or conductive agent is needed in the assembly process.
The general process is as follows:
(1) drying a liquid transfer gun, a diaphragm, a positive electrode shell, a negative electrode shell and the like used for assembling the battery in a vacuum oven at 60 ℃;
(2) the battery assembly sequence is as follows: the lithium battery comprises a negative electrode shell, an elastic sheet, a gasket, a lithium sheet, electrolyte, a diaphragm, electrolyte, a positive electrode sheet, a gasket and a positive electrode shell, wherein the electrolyte on two sides of the diaphragm is 20 mu L and has the composition of 1.0M LiTFSI and 1% LiNO3In a solution of DME: DOL (DME: DOL ═ 1:1 Vol%);
(3) after assembly, the cells were compacted using a button cell sealer (positive casing down, negative casing up) for subsequent testing.
In addition, the carbon-sulfur composite membrane can be used as a positive electrode material of batteries such as sodium-sulfur batteries and zinc-sulfur batteries, and is very important for improving the performance of the batteries. In addition, the film can be applied to the fields of gunpowder, medicament, medicine synthesis and the like, and has very wide and good application prospect.
Product characterization and performance testing
Analysis from the thermogravimetric plot of fig. 1 yields: the sulfur loading of the carbon-sulfur composite film obtained in example 1 was 60%. The carbon-sulfur composite film of example 1 was applied to example 7, a wafer having a diameter of 1.1cm and a thickness of 100 μm was selected as the electrode piece, the weight of the electrode piece was 7.9 g, and the calculated area sulfur loading was 4.99 mg/cm2The high area sulfur-carrying capacity is beneficial to that the lithium-sulfur battery does not need to use a bonding agent and a conductive agent in the manufacturing process, so that the area capacity and the energy density of the lithium-sulfur battery are improved, and the battery also has higher and more stable charging and discharging specific capacity and longer cycling stability correspondingly.
As can be seen from the SEM image of fig. 2: the carbon-sulfur composite film has a nano-pore structure on the surface (note: sulfur cannot be seen in an SEM picture, because a sulfur simple substance is rapidly volatilized by a high-energy electron beam under the test vacuum environment of the SEM), the sulfur can be completely coated by the carbon, a certain pore gap is left, the pore is left after the nano sulfide is oxidized and decomposed, enough space is left for the volume change of the sulfur in the lithiation and lithium removal processes, and the electrode pulverization is effectively avoided.
Fig. 3 is a graph showing the change in specific discharge capacity of the battery of example 7, as seen from fig. 3: the lithium-sulfur battery prepared by using the carbon-sulfur composite film provided by the invention as the anode material has higher and more stable charge-discharge specific capacity and longer cycle stability, and the cycle performance of the anode material after nitrogen doping is further improved. The charge curves of the upper nitrogen-doped and undoped materials coincide, but the discharge curve has significantly better cycle stability, especially after 700 charge-discharge cycles. The analysis may be due to: the nitrogen-doped carbon-sulfur composite membrane has better adsorption performance of nitrogen to sulfur, so that the nitrogen-doped carbon-sulfur composite membrane has better cycle performance when being applied to a lithium-sulfur battery.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It should be understood by those skilled in the art that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by using equivalent alternatives or equivalent variations fall within the scope of the present invention.
Claims (10)
1. The carbon-sulfur composite film is characterized in that the internal structure of the material is porous carbon coated with elemental sulfur, wherein the carbon is porous, and the elemental sulfur is distributed in pore channels of the carbon.
2. The carbon-sulfur composite film according to claim 1, wherein the film is a self-supporting carbon-sulfur composite film containing in-situ generated sulfur, and the film thickness is 1 to 1000 μm.
3. The carbon-sulfur composite film according to claim 1, wherein the elemental sulfur is 10-80% by mass, the elemental sulfur is sulfur nanoparticles, and the particle size is 1-1000 nm.
4. The method for preparing a carbon-sulfur composite film according to claim 1, comprising the steps of:
s1, mixing a sulfur precursor, a carbon precursor, a solvent, an adhesive and a defoaming agent, adding into a ball mill, and ball-milling to obtain slurry for tape casting;
s2, carrying out vacuum defoaming treatment on the slurry prepared in the step S1, and then carrying out tape casting on a casting machine to prepare a blank film;
s3, cutting the embryonic membrane prepared in the step S2 into pieces and then drying the embryonic membrane;
s4, performing high-temperature carbonization treatment on the dried embryonic membrane prepared in the step S3;
s5, soaking the film prepared in the step S4 in an oxidizing solution to oxidize the negative 2-valent sulfur into elemental sulfur in situ;
and S6, washing the film prepared in the step S5 for multiple times by deionized water, and then drying to obtain the carbon-sulfur composite film.
5. The method for preparing a carbon-sulfur composite film according to claim 4, wherein in step S1, the sulfur precursor is nano-sulfide particles with a particle size of 1-1000 nm; preferably, the carbon precursor is selected from one or more of sucrose, glucose, phenolic resin and asphalt, and the mass ratio of the carbon precursor to the sulfur precursor in the casting material is 1/20-20/1; preferably, the solvent is one of water, acetone or alcohol, and the mass fraction of the solvent in the casting material is 40% -90%; preferably, the adhesive is selected from one or more of polyvinyl butyral (co-vinyl alcohol-co-vinyl acetate), polyacrylamide, polyvinyl alcohol (PVA) and partially hydrolyzed polyvinyl alcohol (PVA), and the mass ratio of the sulfur precursor to the adhesive is 1/10-10/1; preferably, the defoaming agent is n-butyl alcohol and accounts for 0.1-10% of the mass fraction of the casting material.
6. The method of claim 4, further comprising a plasticizer selected from one or more of polyethylene glycol, polyol and polyamine in a mass ratio of the plasticizer to the sulfur precursor of 1/10 to 10/1, or 1/5 to 5/1, or 1/1 to 3/1 in the step S1.
7. The method as claimed in claim 4, further comprising a surfactant selected from the group consisting of: one or more of poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide) block copolymer (PEO-PPO-PEO), polysorbate 80, and partially hydrolyzed polyvinyl alcohol (PVA), wherein the mass ratio of the surfactant to the carbon precursor is 1/100 to 100/1 or 1/10 to 10/1.
8. The method as claimed in claim 4, wherein step S1 further comprises a reinforcing material selected from the group consisting of: one or more of carbon nanotubes, carbon fibers, graphene and graphene oxide; preferably, a dopant is also included, the dopant being selected from the group consisting of: one or more of a nitrogen precursor, a phosphorus precursor, a boron precursor, and a sulfur precursor.
9. The method of claim 4, wherein in step S2, the casting speed is 0.01-10 m/min, the blade height is 50-5000 μm; preferably, in step S4, the carbonization is performed at a temperature between 500 ℃ and 1500 ℃, and the carbonization is performed in a protective atmosphere, wherein the protective atmosphere is an atmosphere of nitrogen, helium, argon or a mixture thereof; preferably, in step S5, the oxidizing solution is selected from one of ferric sulfate, ferric cyanide, ferric chloride, ferric ammonium sulfate, sodium hypochlorite, potassium permanganate, and sodium hypochlorite.
10. A lithium sulfur battery, a sodium sulfur battery or a zinc sulfur battery prepared by using the carbon sulfur composite thin film according to any one of claims 1 to 3 as a positive electrode material.
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